(Table 2) Planktonic to benthic foraminifera ratios at DSDP Site 63-468

In recent years there has been considerable discussion concerning the biostratigraphic correlations between planktonic zonations and the classical Neogene California benthic foraminiferal stages. One of the primary objectives of IPOD Leg 63 was to investigate these correlations and to determine the possibility of temporal variation of the benthic stages between California land sections and the outer Continental Borderland. In addition, it was anticipated that analyses of the benthic foraminiferal faunas at Site 468 would provide critical information on the paleoenvironmental history of the outer borderland. The provincial benthic Neogene foraminiferal stages were established by Kleinpell (1938) for the Miocene and Natland (1952) for the Pliocene-Pleistocene; both are well-documented in designated type sections. These stages have been used for interbasinal correlations, although time-transgressive problems have been suggested by several authors (Bandy, 1971; Ingle, 1967, 1973; Crouch and Bukry, 1979). An important biostratigraphic sequence occurs at Site 468, significant because of its relatively shallow depth of approximately 1700 meters. The samples yield well-preserved benthic foraminiferal faunas throughout most of the Neogene sequence and are accompanied by abundant well-preserved calcareous and siliceous planktonic assemblages. It is this co-occurrence of both planktonic and benthic faunas that enables the correlation of outer continental margin sediments with those of the classical land-based sections of southern California.

(Table 1) Mineralogy of veins in basalts at DSDP Hole 61-462A

Numerous veins are present in basalts recovered from Hole 462A, Leg 61 of the Deep Sea Drilling Project. Three mineral assemblages are recognized and stratigraphically controlled. These assemblages are (1) a zeolite-bearing, quartz-poor assemblage which occurs from Core 44 to the bottom of the hole and contains smectite, clinoptilolite, calcite, pyrite, ± chabazite, ± analcime, ± quartz, ± apophyllite, ± talc (?); (2) a quartz-rich, pyrite-bearing assemblage, found between Cores 19 and 29, which contains smectite, calcite, quartz, and pyrite; and (3) a quartz-rich, celadonite-bearing assemblage which occurs from Cores 14 through 17 and contains smectite, calcite, quartz, celadonite, and Fe oxide. These data are interpreted to represent two episodes of vein mineral formation with an oxidative overprint on the more recent. The first episode followed the outpourings of basaltic lavas onto the sea floor. Zeolite-bearing veins were formed at elevated temperatures under low PCO2 while the thermal gradient was high and before a cover of calcareous sediments had formed. The second mineralization episode followed injection of basalt and microdiabase sills into a thick layer of sediments, and produced all the vein minerals now occurring between Cores 14 and 29. These veins formed at lower temperature and higher PCO2 than zeolite-bearing veins. The presence of pyrite indicates a nonoxidative environment. After the initial formation of these veins, oxygenated seawater diffused through the sedimentary cover and oxidized the pyrite and smectite, forming celadonite and Fe oxides.

(Table 1) Physical properties of basalts from DSDP Holes 69-504B and 70-504B

A detailed study of physical properties was made on core samples from Deep Sea Drilling Project Hole 504B. The measured properties are density, porosity, sonic velocity, electrical resistivity, and fluid permeability. Basalts from this young oceanic crust have higher density and sonic velocity than the average DSDP basalts. Porosity (and temperature) dependences of physical properties are given by V = Vo - a-phi; roo = roo-0 exp(E*/RT)phi**-q; k = k0' phi**2q-1; where V is the sonic velocity (km/s), Vo = 6.45 (km/s), a = 0.111 (km/s %), phi is the porosity (%), roo is the electrical resistivity (ohm m), roo-0 = 0.002 (ohm m), E* = 2.7 (Kcal/mol) for fresh basalts, RT has its usual meaning, q = 1.67 ± 0.27, k is the permeability, k0' = (1 to about 10) x 10**-12 (cm**2). Porosity distribution in the crust in this area is estimated by combining the seismic velocity distribution and velocity-porosity relation. Because of the rapid decrease in porosity with depth, resistivity increases and permeability decreases rapidly with depth. The decreasing rate of permeability with increasing depth is approximately given by k(cm**2) = 2 x 10**-10 exp(-z (km)/0.3).